1. Field
The present inventive concept relates to an apparatus and method of operating a memory device.
2. Description of the Related Art
Memory devices are classified into volatile memory devices and nonvolatile memory devices. The volatile memory devices lose stored data when the power supply is turned off. Examples of the volatile memory devices include static random access memories (SRAMs), dynamic random access memories (DRAMs), and synchronous dynamic random access memories (SDRAMs). On the other hand, the nonvolatile memory devices retain stored data even when the power supply is interrupted.
Examples of the nonvolatile memory devices include flash memories, read-only memories (ROMs), programmable read-only memories (PROMs), erasable programmable read-only memories (EPROMs), electrically erasable programmable read-only memories (EEPROMs), and resistive memories (e.g., phase-change random access memories (PRAMs), ferroelectric random access memories (FRAMs), and resistive random access memories (RRAMs)).
A flash memory may perform an electric erase operation on a block-by-block basis and a program operation on a bit-by-bit basis.
Threshold voltages of a plurality of programmed memory cells included in a flash memory may change due to various causes. A change in the threshold voltages of the memory cells can undermine the reliability of read data.